The Organic Light Emitting Display (OLED) display, which is also named as Organic electroluminescent display, is a new flat panel display device. Because it possesses many outstanding properties of self-illumination, low driving voltage, high luminescence efficiency, short response time, high clarity and contrast, near 180° view angle, wide range of working temperature, applicability of flexible display and large scale full color display. The OLED is considered as the most potential display device in the industry.
Because the OLED display device possesses advantages of self-illumination, simple structure with low cost, fast response speed, wide view angle, high color saturation, high contrast, being light and flexible, more and more smart phones and the wearable devices start using the OLED display device.
The OLED display element generally comprises a substrate, an anode located on the substrate, a Hole Injection Layer located on the anode, a Hole Transporting Layer located on the Hole Injection Layer, an emitting layer located on the Hole Transporting Layer, an Electron Transport Layer located on the emitting layer, an Electron Injection Layer located on the Electron Transport Layer and a Cathode located on the Electron Injection Layer. The principle of the OLED element is that the illumination generates due to the carrier injection and recombination under the electric field driving of the semiconductor material and the organic semiconductor illuminating material. Specifically, with a certain voltage driving, the Electron and the Hole are respectively injected into the Electron and Hole Transporting Layers from the cathode and the anode. The Electron and the Hole respectively migrate from the Electron and Hole Transporting Layers to the Emitting layer and bump into each other in the Emitting layer to form an exciton to excite the emitting molecule. The latter can illuminate after the radiative relaxation.
Specifically, the full color display OLED display device generally comprises a plurality of red OLED elements, a plurality of green OLED elements, a plurality of blue OLED elements. The light emitting layers of the red OLED elements, the green OLED elements, the blue OLED elements respectively are red light emitting layers, green light emitting layers, blue light emitting layers. For making the red OLED elements, the green OLED elements, the blue OLED elements respectively achieve the optimized luminous efficiencies, the hole transporting layers of the OLED elements of different colors are set to have different thicknesses to adjust the light distances of the red light, the green light, the blue light. The Fabry-Perot resonance principle is used to calculate the best light distances to make the red light emitting layers, green light emitting layers, blue light emitting layers respectively at the positions of the second antinodes, and thus, the luminous efficiencies reach the maximum. It requires that the hole transporting layers of the red OLED elements, the green OLED elements, the blue OLED elements need to use three different FMMs (Fine Metal Mask) to be manufactured with three evaporation processes. Accordingly, the production cost is increased, and the process time is extended. Meanwhile, the product yield decreases due to the complexity of the process.